BACKGROUND: Increasing medical school faculty diversity is an urgent priority. National Institutes of Health (NIH) diversity supplements, which provide funding and career development opportunities to individuals underrepresented in research, are an important mechanism to increase faculty diversity. OBJECTIVE: Analyze diversity supplement utilization by medical schools. DESIGN: Retrospective cohort study. PARTICIPANTS: All R01 grant-associated diversity supplements awarded to medical schools from 2005 to 2020. Diversity supplements were identified using the publicly available NIH RePORTER database. MAIN MEASURES: Main measures were the number of R01-associated diversity supplements awarded to medical schools each year by medical school NIH funding status and the number of R01-associated diversity supplements awarded to individual medical schools in the NIH top 40 by funding status. We also examined the percentage of R01 grants with an associated diversity supplement by NIH funding status and individual medical school in the NIH top 40. KEY RESULTS: From 2005 to 2020, US medical school faculty received 1389 R01-associated diversity supplements. The number of diversity supplements awarded grew from 2012 to 2020, from ten to 187 for top 40 schools, and from seven to 83 for non-top 40 schools. The annual growth rate for diversity supplement awards at NIH top 40 schools (44.2%) was not significantly different than the annual growth rate among non-top 40 schools (36.2%; p = 0.68). From 2005 to 2020, the highest number of diversity supplements that an individual medical school received was 56 and the lowest number was four (mean = 24.6, SD = 11.7). The highest percentage of R01 grants with an associated diversity supplement received by a school was 4.5% and the lowest percentage was 0.79% (mean = 2.3%, SD = 0.98). CONCLUSION: Medical schools may be missing an opportunity to address the continuing shortage of individuals historically underrepresented in biomedical science and should consider additional mechanisms to enhance diversity supplement utilization.